Aer Receptors Influence the Pseudomonas chlororaphis PCL1606 Lifestyle

Abstract

Pseudomonas chlororaphis PCL1606 (PcPCL1606) is a rhizobacterium isolated from avocado roots, which is a favorable niche for its development. This strain extensively interacts with plant roots and surrounding microbes and is considered a biocontrol rhizobacterium. Genome sequencing has shown the presence of thirty-one potential methyl-accepting chemotaxis proteins (MCPs). Among these MCPs, two candidates are putative functional aerotaxis receptors, encoded at locus PCL1606_41090 ( aer 1-1) and locus PLC1606_20530 ( aer 1-2), that are homologous to the Aer receptor of Pseudomonas aeruginosa strain PaO1. Single- and double-deletion mutants in one or both genes have led to motility deficiencies in oxygen-rich areas, particularly reduced swimming motility compared with that of wildtype PcPCL1606. No differences in swarming tests were detected, and less adhesion by the aer double mutant was observed. However, the single and double mutants on avocado plant roots showed delayed biocontrol ability. During the first days of the biocontrol experiment, the aer -defective mutants also showed delayed root colonization. The current research characterizes the presence of aer transductors on P. chlororaphis . Thus, the functions of the PCL1606_41090 and PCL1606_20530 loci, corresponding to genes aer 1-1 and aer 1-2, respectively, are elucidated.

Identification of Aerotaxis Receptor Proteins Involved in Host Plant Infection by <i>Pseudomonas syringae</i> pv. <i>tabaci</i> 6605

“…1 D). This topological organization is common in other aerotaxis transducers, such as Aer of Pseudomonas putida ( Nichols and Harwood, 2000 ) and P. aeruginosa ( Hong et al , 2004 ), Aer-1 of Vibrio cholerae ( Boin and Häse, 2007 ), Aer-1 and Aer-2 of Ralstonia solanacearum ( Yao and Allen, 2007 ), and Aer1-1 and Aer1-2 of Pseudomonas chlororaphis ( Arrebola and Cazorla, 2020 ). On the other hand, atypical Aer transducers were also found in AerC of Azospirillum brasilense ( Xie et al , 2010 ) and Aer-2 of V. cholerae ( Boin and Häse, 2007 ) and P. aeruginosa ( Hong et al , 2004 ).…”

“…In plant-infecting bacteria, chemotaxis towards plant-derived compounds is considered to facilitate entry into plants through natural openings or wounds ( Matilla and Krell, 2018 ). Aerotaxis itself has been associated with effective and efficient attachment and colonization by the biocontrol bacteria A. brasilense ( Greer-Phillips et al , 2004 ) and P. chlororaphis ( Arrebola and Cazorla, 2020 ) and the soil-borne pathogen R. solanacearum ( Yao and Allen, 2007 ). We assume that Pta 6605, as a foliar plant pathogen, also performs aerotaxis to reach a potential niche that supports its survival on the harsh foliar plane.…”

Chemotaxis of Beneficial Rhizobacteria to Root Exudates: The First Step towards Root–Microbe Rhizosphere Interactions

“…A representative example is that of Pseudomonas chlororaphis that was isolated from avocado roots and that showed biocontrol activity towards the pathogen Rosellinia necatrix. The former organism produces the highly redox-active compound phenazine causing energy taxis involving multiple Aer receptors [56].…”

Isolation and Characterization of Pseudomonas chlororaphis Strain ST9; Rhizomicrobiota and in Planta Studies

“…P. chlororaphis is currently classified into four subspecies, namely chlororaphis , aureofaciens , aurantiaca , and piscium [ 15 , 16 ]. Several strains of P. chlororaphis have shown potential for application as plant probiotics [ 17 , 18 , 19 ] due to their rhizosphere colonization abilities and plant-associated beneficial phenotypes such as chemotaxis and motility [ 20 ], biofilm formation [ 21 ], P solubilization [ 22 ], ACC deaminase [ 23 ], IAA production [ 24 , 25 ] and biocontrol. P. chlororaphis strains produce different antifungal compounds such as Prn (pyrrolnitrin), PCN (phenazine-1-carboxamide), PCA (phenazine-1-carboxylic acid), 2-OH-PHZ (2-hydroxyphenazine), HPR (2-hexyl-5-propyl-alkylresorcinol) and HCN (hydrogen cyanide).…”